Staphylococcus aureus resists opsonophagocytosis partly through a surface component that binds the Fc portion of IgG at the hinge-proximal site. This component is:
- A Teichoic acid
- B Clumping factor (bound coagulase)
- C Protein A ✓
- D Polysaccharide capsule
Correct answer: C. Protein A
Explanation
Protein C is a cell wall surface protein of S. aureus that binds the Fc region of IgG1, IgG2 and IgG4, leaving the Fab ends pointing outward. The bacterium therefore coats itself with antibody oriented wrongly for opsonisation and complement activation, evading phagocytosis. Clumping factor binds fibrinogen, teichoic acid aids adhesion, and the capsule is antiphagocytic by a different route, but none of these bind IgG Fc.
Reference: Jawetz, Melnick and Adelberg's Medical Microbiology, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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